Pyramidalization and reactivity of trigonal centers. X-ray crystal structure analysis of two silyl enol ethers from 1-benzoyl- and 1-(methoxycarbonyl)-2-tert-butyl-3,5-dimethyl-4-imidazolidinone (reagents for amino acid synthesis)

Article abstract of DOI:10.1021/ja00005a049

The title structures, which may be considered models for the Li enolates, contain three trigonal centers (N1, N3, C5) with unusually large pyramidalization. This leads to an all-trans arrangement of four substituents with respect to the plane of the five-